U.S. patent application number 11/576133 was filed with the patent office on 2008-03-13 for radio communication device and radio communication method.
This patent application is currently assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.. Invention is credited to Ayako Horiuchi, Akihiko Nishio.
Application Number | 20080063097 11/576133 |
Document ID | / |
Family ID | 36119048 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080063097 |
Kind Code |
A1 |
Horiuchi; Ayako ; et
al. |
March 13, 2008 |
Radio Communication Device and Radio Communication Method
Abstract
There is provided a radio communication device capable of
suppressing increase of power consumption of a relay station
device. In this device, a channel information extraction unit (31)
extracts channel information (channel information in the mobile
station device of the signal transmitted from the base station
device) from the reception signal from a base station device; a sub
carrier selection unit (32) selects a sub carrier of low received
quality according to the channel information; a relay data
extraction unit (33) extracts data to be relay-transmitted
according to the selection result in the sub carrier selection unit
(32); and a sub carrier allocation unit (35) allocates data to be
relay-transmitted to the sub carrier for relay transmission.
Inventors: |
Horiuchi; Ayako; (Kanagawa,
JP) ; Nishio; Akihiko; (Kanagawa, JP) |
Correspondence
Address: |
STEVENS, DAVIS, MILLER & MOSHER, LLP
1615 L. STREET N.W.
SUITE 850
WASHINGTON
DC
20036
US
|
Assignee: |
MATSUSHITA ELECTRIC INDUSTRIAL CO.,
LTD.
1006, Oaza Kadoma, Kadoma-shi
Osaka
JP
571-8501
|
Family ID: |
36119048 |
Appl. No.: |
11/576133 |
Filed: |
September 29, 2005 |
PCT Filed: |
September 29, 2005 |
PCT NO: |
PCT/JP05/18019 |
371 Date: |
March 27, 2007 |
Current U.S.
Class: |
375/260 |
Current CPC
Class: |
H04L 5/0048 20130101;
H04L 5/0007 20130101; H04L 5/0046 20130101; H04B 7/15542 20130101;
H04L 5/006 20130101 |
Class at
Publication: |
375/260 |
International
Class: |
H04L 27/28 20060101
H04L027/28 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 29, 2004 |
JP |
2004-285468 |
Claims
1. A radio communication apparatus comprising: a receiving section
that receives a first multicarrier signal comprised of a plurality
of subcarriers, from a first radio communication apparatus; a
subcarrier selection section that selects part of the plurality of
subcarriers; an extraction section that extracts, from the first
multicarrier signal, a subcarrier signal allocated to the part of
the plurality subcarriers, in accordance with a selection result in
the subcarrier selection section; and a transmission section that
transmits a second multicarrier signal including the subcarrier
signal, to a second radio communication apparatus.
2. The radio communication apparatus according to claim 1, wherein
the subcarrier selection section selects a subcarrier which has
lower received quality than predetermined quality in the second
radio communication apparatus.
3. The radio communication apparatus according to claim 1, wherein
the transmission section allocates the subcarrier signal to a
subcarrier constituting the second multicarrier signal using the
same mapping as the mapping of the first multicarrier signal.
4. The radio communication apparatus according to claim 1, wherein
the transmission section allocates the subcarrier signal to a
subcarrier having higher received quality than predetermined
quality in the second radio communication apparatus.
5. The radio communication apparatus according to claim 1, wherein:
the selection section selects the part of the plurality of
subcarriers in a plurality of frames; the extraction section
extracts the subcarrier signal allocated to the part of the
plurality of subcarriers in the plurality of frames; and the
transmission section allocates a plurality of subcarrier signals
extracted in the plurality of frames, to subcarriers which differ
from one another.
6. The radio communication apparatus according to claim 1, wherein
the subcarrier selection section selects the part of the plurality
subcarriers from a managing subcarrier.
7. The radio communication apparatus according to claim 1, wherein
the transmission section transmits the second multicarrier signal
in synchronization with another radio communication apparatus.
8. The radio communication apparatus according to claim 1, further
comprising a pilot selection section that selects whether or not to
insert a pilot signal into the second multicarrier signal at a
predetermined period or a predetermined timing.
9. A radio communication method comprising: a receiving step of
receiving a first multicarrier signal comprised of a plurality of
subcarriers, from a first radio communication apparatus; a
subcarrier selecting step of selecting part of the plurality of
subcarriers; an extracting step of extracting, from the first
multicarrier signal, a subcarrier signal allocated to the part of
the plurality of subcarriers, in accordance with a selection result
in the subcarrier selecting step; and a transmitting step of
transmitting a second multicarrier signal including the subcarrier
signal, to a second radio communication apparatus.
10. A radio communication system comprising: a first radio
communication apparatus that transmits a first multicarrier signal
comprised of a plurality of subcarriers; and a second radio
communication apparatus and a third radio communication apparatus
that receive the first multicarrier signal, wherein: the third
radio communication apparatus selects part of the plurality of
subcarriers, extracts a subcarrier signal allocated to the part of
the plurality of subcarriers from the first multicarrier signal,
and transmits a second multicarrier signal including the subcarrier
signal, to the second radio communication apparatus; and the second
radio communication apparatus combines the first multicarrier
signal and the second multicarrier signal.
Description
TECHNICAL FIELD
[0001] The present invention relates to a radio communication
apparatus and radio communication method, and more particularly, to
a radio communication apparatus and radio communication method in a
communication network which employs multicarrier transmission such
as OFDM (Orthogonal Frequency Division Multiplex) scheme or the
like.
BACKGROUND ART
[0002] Recently, with the multimediatization of information in
mobile communication systems as represented by mobile phones or the
like, it is becoming popular to transmit not only audio data, but
also large amounts of still picture data, motion picture data and
the like. To realize the transmission of large amounts of data, an
approach is being broadly investigated according to which a
high-frequency radio band is used to obtain a high-transmission
rate.
[0003] However, in the case of using a high-frequency radio band,
while a high transmission rate can be expected at a short distance,
attenuation due to transmission distance is significant. For this
reason, in the case of expanding this to a real system, for
instance, the coverage area of a base station becomes small, which
requires that a larger number of base stations to be provided.
Since the set-up of base stations involves large costs, a
technology is strongly required for realizing communication
services while suppressing an increase in the number of base
stations.
[0004] As a conventional technology related to this, there exists
the technology described in Patent Document 1, for example. In the
conventional technology of this Patent Document 1, a communication
network of cellular-dedicated radio channels which are formed
between a base station and a mobile station, and an ad-hoc network
formed between mobile stations are both used to combine signals,
whereby an improvement of the diversity effect is obtained. [0005]
1 Patent Document 1: Japanese Patent Application Laid-Open No.
2001-189971
DISCLOSURE OF INVENTION
Problems to be Solved by the Invention
[0006] However, in the conventional technology described in Patent
Document 1, since the mobile stations forming the ad-hoc network
carry out an processing of relaying to other mobile stations, while
carrying out the required processings locally, a problem existed
that the amount of power consumption increases.
[0007] It is therefore an object of the present invention to
provide a radio communication apparatus and a radio communication
method capable of suppressing an increase in the power consumption
of a radio communication apparatus that carries out a relay.
Means for Solving the Problem
[0008] In accordance with one aspect of the invention, the radio
communication apparatus of the present invention adopts a
configuration that includes: a receiving section that receives a
first multicarrier signal comprised of a plurality of subcarriers,
from a first radio communication apparatus; a subcarrier selection
section that selects part of the plurality of subcarriers; an
extraction section that extracts, from the first multicarrier
signal, a subcarrier signal allocated to the part of the plurality
subcarriers, in accordance with a selection result in the
subcarrier selection section; and a transmission section that
transmits a second multicarrier signal including the subcarrier
signal, to a second radio communication apparatus.
[0009] According to the above configuration, the multicarrier
signal transmitted from the first radio communication apparatus can
be selected for each subcarrier and relayed, and therefore, the
amount of transmission data is reduced compared to the case that
all subcarriers are relayed, which makes it possible to reduce the
transmission power of the radio communication apparatus that
carries out relay-transmission.
ADVANTAGEOUS EFFECT OF THE INVENTION
[0010] This invention makes it possible to suppress an increase in
the power consumption of a radio communication apparatus that
carries out relay-transmission.
BRIEF DESCRIPTION OF DRAWINGS
[0011] FIG. 1 is a configuration diagram showing a mobile
communication system according to embodiment 1;
[0012] FIG. 2 is a sequence diagram according to embodiment 1;
[0013] FIG. 3A is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 1;
[0014] FIG. 3B is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 1;
[0015] FIG. 3C is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 1;
[0016] FIG. 3D is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 1;
[0017] FIG. 4 is a block diagram showing a configuration of a
mobile station apparatus according to embodiment 1;
[0018] FIG. 5 is a flow chart for a channel information generation
processing of the mobile station apparatus, according to embodiment
1;
[0019] FIG. 6 is a block diagram showing a configuration of a relay
station apparatus according to embodiment 1;
[0020] FIG. 7 is a flow chart for a relay processing of a relay
station apparatus according to embodiment 1;
[0021] FIG. 8 is a block diagram showing a configuration of a base
station apparatus according to embodiment 1;
[0022] FIG. 9 is a flow chart for a relay processing of the base
station apparatus according to embodiment 1;
[0023] FIG. 10 is a configuration diagram of a mobile communication
system according to embodiment 2;
[0024] FIG. 11 is a sequence diagram according to embodiment 2;
[0025] FIG. 12 is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 2;
[0026] FIG. 13 is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 2;
[0027] FIG. 14 is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 2;
[0028] FIG. 15 is a block diagram showing a configuration of a
relay station apparatus according to embodiment 2;
[0029] FIG. 16 is a flow chart showing a relay processing for the
relay station apparatus according to embodiment 2;
[0030] FIG. 17 is a configuration diagram of a mobile communication
system according to embodiment 3;
[0031] FIG. 18 is a sequence diagram according to embodiment 3;
[0032] FIG. 19A is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0033] FIG. 19B is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0034] FIG. 19C is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0035] FIG. 19D is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0036] FIG. 19E is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0037] FIG. 19F is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 3;
[0038] FIG. 20 is a block diagram showing a configuration of a
relay station apparatus according to embodiment 3;
[0039] FIG. 21 is a flow chart for a relay processing of the relay
station apparatus according to embodiment 3;
[0040] FIG. 22 is a configuration diagram of a mobile communication
system according to embodiment 4;
[0041] FIG. 23 is a sequence diagram according to embodiment 4;
[0042] FIG. 24A is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 4;
[0043] FIG. 24B is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 4;
[0044] FIG. 24C is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 4;
[0045] FIG. 24D is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 4;
[0046] FIG. 24E is a diagram showing an example of a received
intensity level for each subcarrier, according to embodiment 4;
[0047] FIG. 24F is a diagram showing an example of a received
intensity level for each subcarrier according to embodiment 4;
[0048] FIG. 25 is a diagram showing a pilot signal according to
embodiment 4;
[0049] FIG. 26 is a block diagram showing a configuration of a
relay station apparatus according to embodiment 4;
[0050] FIG. 27 is a flow chart for a relay processing of the relay
station apparatus according to embodiment 4; and
[0051] FIG. 28 is a diagram showing a pilot signal according to
embodiment 4.
BEST MODE FOR CARRYING OUT THE INVENTION
[0052] Now, embodiments of the present invention will be described
in detail with reference to the accompanying drawings. A radio
communication apparatus to be described hereinafter is a radio
communication apparatus that transmits a multicarrier signal
received from a first radio communication apparatus to a second
radio communication apparatus, and is adapted for installation in a
radio relay station apparatus, for example, to be used in a mobile
communication system.
[0053] Hereinafter, the radio communication apparatus of the
present invention is described as a relay station apparatus, the
first radio communication apparatus as a base station apparatus and
the second radio communication apparatus as a mobile station
apparatus.
Embodiment 1
[0054] As shown in FIG. 1, the mobile communication system
according to the present embodiment is comprised of a mobile
station apparatus 100, a relay station apparatus 150 and a base
station apparatus 200.
[0055] Base station apparatus 200 instructs in advance relay
station apparatus 150 to relay a signal to mobile station apparatus
100. Also, base station apparatus 200 holds corresponding
information of the identification information for mobile station
apparatus 100 and relay station apparatus 150, and relay station
apparatus 150 holds identification information of mobile station
apparatus 100, which is the object of relaying. Also, the
identification information of relay station apparatus 150 may also
be held in mobile station apparatus 100.
[0056] Next, the overall processing will be described using the
sequence diagram shown in FIG. 2.
[0057] Base station apparatus 200 transmits a multicarrier signal
to mobile station apparatus 100 and relay station apparatus 150
(processings (1) and (2)) Mobile station apparatus 100 generates
channel information assigning a level to the received quality, for
each subcarrier constituting the multicarrier signal received from
base station apparatus 200. The present embodiment shows an example
where received intensity level is used as received quality. Next,
mobile station apparatus 100 reports the generated channel
information to base station apparatus 200 (processing (3)). Base
station apparatus 200 reports the reported channel information to
relay station apparatus 150, before relay station apparatus 150
transmits relay data to mobile station apparatus 100 (processing
(4)). In accordance with the reported channel information, relay
station apparatus 150 selects, from the multicarrier signal
received from base station apparatus 200, a subcarrier having lower
received quality than a predetermined level, extracts a subcarrier
signal corresponding to the subcarrier selected from the
multicarrier signal addressed to mobile station apparatus 100 and
received in processing (2), and relay-transmits it to mobile
station apparatus 100 as multicarrier signal (processing (5)).
[0058] Next, examples showing the received intensity level of a
received signal received at mobile station apparatus 100 and relay
station apparatus 150 are shown in FIGS. 3A to 3D. In FIGS. 3A to
3D, the numerical symbols 1 to 8 on the horizontal axis show
subcarrier numbers, an example where the multicarrier signal is
comprised of subcarriers 1 to 8. The same symbols are used in the
following embodiments, as well.
[0059] FIG. 3A shows the received intensity level for each
subcarrier of the signal transmit from base station apparatus 200
to mobile station apparatus 100 in processing (1) of FIG. 2; FIG.
3B shows the received intensity level for each subcarrier of the
signal transmit from base station apparatus 200 to relay station
apparatus 150 in processing (2) of FIG. 2; FIG. 3C shows the
received intensity level for each subcarrier of the signal
transmitted from relay station apparatus 150 to mobile station
apparatus 100 in processing (5) of FIG. 2; FIG. 3D shows the
received intensity level for each subcarrier after the signal
combination in mobile station apparatus 100, respectively. The
received intensity level differs for every subcarrier due to the
influence of the frequency-selective fading propagation.
[0060] From the signal shown in FIG. 3A, the fifth and seventh
subcarriers are selected as subcarriers of low-received quality
(which do not reach a target received intensity level). According
to this selection result, relay station apparatus 150
relay-transmits, as shown in FIG. 3C, only the fifth and seventh
subcarriers from the received signal shown in FIG. 3B. Mobile
station apparatus 100 combines the signal received in processing
(1) of FIG. 2 and shown in FIG. 3A and the signal received in
processing (5) of FIG. 2 and shown in FIG. 3C, to obtain the signal
shown in FIG. 3D.
[0061] Next, the configurations of mobile station apparatus 100,
relay station apparatus 150 and base station apparatus 200 will be
described.
[0062] FIG. 4 is a block diagram showing a configuration of mobile
station apparatus 100 according to the present embodiment. Mobile
station apparatus 100 of the present embodiment is comprised of:
antenna 18; radio receiving section 19 that receives a radio
signal; GI removing section 20 that removes a guard interval (GI);
FFT section 21 that carries out an FFT processing; P/S section 22
that carries out P/S conversion; channel estimation section 23 that
carries out channel estimation; demodulation section 24 that
carries out demodulation of the received signal; combination
section 27 that combines the demodulated signals; decoding section
25 that carries out decoding; channel information generation
section 26 that generates channel information; coding section 11
that carries out encoding; modulation section 12 that carries out
modulation; S/P section 13 that carries out S/P conversion; IFFT
section 14 that carries out IFFT processing; GI inserting section
15 that inserts a GI; and radio transmission section 16 that
transmits a radio signal.
[0063] Next, the processing of mobile station apparatus 100 shown
in FIG. 4 will be described. The processing is broadly classified
into reception processing and transmission processing.
[0064] First, the reception processing will be described. Antenna
18 receives a radio signal from base station apparatus 200 or from
other mobile station such as relay station apparatus 150 or the
like. Radio receiving section 19 subjects the received signal to a
radio processing such as down-conversion, to obtain a baseband
signal. GI removing section 20 removes the guard interval. FFT
section 21 carries out an FFT processing in which the received
signal is converted from the time domain to the frequency domain
and the received signal of each subcarrier is inputted to P/S
section 22. P/S section 22 carries out parallel-serial conversion.
The received signal which has been subjected to the parallel-serial
conversion is inputted to channel estimation section 23,
demodulation section 24, and channel information generation section
26. The processing of channel information generation section 26
will be described later. Channel estimation section 23 estimates a
propagation path for each subcarrier and generates a propagation
path estimation value. The propagation path estimation value is
inputted to demodulation section 24. Demodulation section 24
reduces the error caused by the influence of amplitude fluctuation
and phase fluctuation of the propagation path and demodulates the
signal, by dividing the inputted received signal by the propagation
path estimation value. Combination section 27 combines the signal
transmitted from base section device 200 and the signal transmitted
from relay section device 150. The combined signal is inputted to
the decoding section. Decoding section 25 decodes the received
signal and outputs received data.
[0065] Next, the processing of channel information generation
section 26 will be described in detail using the flow chart of FIG.
5. In ST (step) 101, a pilot signal is extracted from the received
signal. In ST102, it is judged whether the received signal is a
signal from the base station or signal from the relay station, and,
when the received signal is a signal from the base station, the
received intensity level is measured for each subcarrier from the
extracted pilot signal. In ST 104, channel information of the
signal from the base station in the mobile station is
generated.
[0066] Next, the transmission processing will be described. Coding
section 11 subjects the inputted time-series transmission data or
the channel information to encoding with turbo code or the like,
and the encoded transmission signal is inputted to modulation
section 12. Depending on the transmission timing of the respective
signals, a control section (not shown) controls which of the
transmission data and the channel information is to be subjected to
the encoding processing. Modulation section 12 subjects the
transmission data to modulation such as QPSK, 16 QAM or the like.
The modulated transmission data is inputted to S/P section 13. S/P
section 13 subjects the transmission signal to serial-parallel
conversion. The transmission signal that has been subjected to the
serial-parallel conversion is inputted to IFFT section 14. IFFT
section 14 carries out an IFFT processing to convert the frequency
domain signal to a time domain signal. The transmission signal
converted to the time domain is inputted to GI inserting section
15. GI inserting section 15 inserts a guard interval into the
transmission signal. The guard interval is inserted in such a way
that the end portion of one frame is copied to the head of the
frame. The transmission signal to which the guard interval has been
added is inputted to radio transmission section 16. Radio
transmission section 16 subjects the transmission signal to a radio
processing such as up-conversion, and the transmission signal
resulting from the radio processing is transmitted from antenna
18.
[0067] FIG. 6 is a block diagram showing a configuration of relay
station apparatus 150 according to the present embodiment. The same
elements as those in FIG. 4 are designated by the same numerical
symbols and description thereof is hereby omitted. Relay station
apparatus 150 according to the present embodiment is comprised of
antenna 18; radio receiving section 19 that receives a radio
signal; GI removing section 20 that removes the GI; FFT section 21
that carries out an FFT processing; P/S section 22 that carries out
P/S conversion; channel estimation section 23 that carries out
channel estimation, demodulation section 24 that carries out
demodulation of the received signal; decoding section 25 that
carries out decoding; relay processing section 37 that extracts a
subcarrier signal to be relayed; IFFT section 14-2 that carries out
an IFFT processing; GI inserting section 15-2 that inserts a guard
interval; radio transmission section 16-2 that transmits the radio
signal; coding section 36 that carries out encoding; modulation
section 12 that carries out modulation; S/P section 13 that carries
out S/P conversion; IFFT section 14-1 that carries out an IFFT
processing; GI inserting section 15-1 that inserts a guard
interval; and a radio transmission section 16-1 that transmits a
radio signal.
[0068] Next, the configuration and processing of relay processing
section 37 will be described in detail. Relay processing section 37
is comprised of channel information extraction section 31 that
extracts channel information from the received signal; subcarrier
selection section 32 that selects a subcarrier to be relayed;
subcarrier selection information storage section 34 that stores
information of the subcarrier selected by subcarrier selection
section 32; relay data extraction section 33 that extracts the
subcarrier signal selected by subcarrier selection section 32, from
the relay data, in accordance with the information stored in
subcarrier selection information storage section 34; and subcarrier
allocation section 35 that allocates subcarriers.
[0069] Next, the processing of relay processing section 37 will be
described using the flow chart of FIG. 7.
[0070] In ST (Step) 151, channel information extraction section 31
extracts channel information from the signal inputted from P/S
section 22 (the signal received from base station apparatus 200).
This channel information is the channel information, in mobile
station apparatus 100, of the signal transmitted from base station
apparatus 200, and relay station apparatus 150 also receives from
base station apparatus 200, together with the channel information,
the identification information of mobile station apparatus 100
which has generated the channel information. The extracted channel
information is inputted to subcarrier selection section 32.
[0071] In ST152, subcarrier selection section 32 selects a
subcarrier having a lower received intensity level than a
predetermined target received intensity level, in accordance with
the extracted channel information. For instance, when channel
information as shown in FIG. 3A is given, since the received
quality of the fifth and seventh subcarriers is low, information
for identifying the fifth and seventh subcarriers is generated as
selection subcarrier information.
[0072] In ST153, these subcarrier selection results are stored, for
each identification information of mobile station apparatus 100, in
subcarrier selection information storage section 34, as subcarrier
selection information (identification information or the like of
selected subcarriers).
[0073] In ST154, relay data extraction section 33 acquires, from
subcarrier selection information storage section 34, subcarrier
selection information which matches the identification information
of mobile station apparatus 100 to which the relay is made, and in
accordance with the acquired subcarrier selection information,
extracts a subcarrier signal to be relay-transmitted and inputs it
to subcarrier allocation section 35.
[0074] In ST155, subcarrier allocation section 35 allocates the
subcarrier signal to be relay-transmitted, to each subcarrier. In
this example, subcarrier allocation section 35 allocates the
subcarrier signal to be relay-transmitted to each subcarrier, by
using the same mapping as the mapping of the multicarrier signal
received by relay station apparatus 150. In other words, the
extracted subcarrier signal is allocated to each subcarrier without
changing the allocation to the subcarriers. Therefore, in mobile
station apparatus 100, it is possible to easily combine the signal
transmitted from base station apparatus 200 with the signal relayed
by relay station apparatus 150.
[0075] FIG. 8 is a block diagram showing a configuration of base
station apparatus 200 according to the present embodiment. The same
elements as those of FIG. 4 are designated by the same numerical
symbols and description thereof is hereby omitted. Base station
apparatus 200 according to the present embodiment receives data
signals from mobile station apparatus 100 or relay station
apparatus 150 and channel information from mobile station apparatus
100, and transmits transmission data addressed to relay station
apparatus 150, transmission data addressed to mobile station
apparatus 100, and channel information addressed to relay station
apparatus 150 and identification information of mobile station
apparatus 100 which has generated that channel information.
[0076] Next, the processings of channel information extraction
section 41 and relay management section 42 of base station
apparatus 200 will be described in detail using the flow chart in
FIG. 9.
[0077] In ST (step) 201, channel information extraction section 41
extracts channel information from the received signal, similar to
channel information extraction section 31 of relay station
apparatus 150 in FIG. 6. Then, it is judged whether the received
signal is channel information. When the received signal is not
channel information, relaying is not carried out. When the received
signal is channel information, the flow proceeds to ST202.
[0078] In ST202, an extraction processing is carried out by channel
information extraction section 41.
[0079] In ST203, relay station apparatus 150 is designated as the
destination of the channel information, from information which
shows which relay station carries out relaying of which mobile
station and which is managed by relay management section 42.
[0080] Next, the channel information whose relay destination has
been designated is inputted to S/P section 13, and is transmitted
to relay station apparatus 150 after a transmission processing has
been carried out.
[0081] In the present embodiment, since the subcarrier to be
relayed by relay station apparatus 150 is limited to a subcarrier
having low received quality between mobile station apparatus 100
and base station apparatus 200 (in other words, a subcarrier
requiring diversity effect), it is possible to reduce the
transmission power of relay station apparatus 150, compared to the
case of relaying all subcarriers.
[0082] Also, mobile station apparatus 100 can combine a signal
transmitted from base station apparatus 200 with a signal
transmitted from relay station apparatus 150 and receive the
signal, the received quality can be improved, and communication
with a reduced bit error rate or with higher data rate becomes
possible.
[0083] In the present embodiment, although the channel information
is transmitted from mobile station apparatus 100 to base station
apparatus 200, and is relayed from base station apparatus 200 back
to relay station apparatus 150, it may be transmitted directly from
mobile station apparatus 100 to relay station apparatus 150.
[0084] In the present embodiment, the channel information is
generated by mobile station apparatus 100. However, it may also be
generated by using the received quality of base station apparatus
200.
[0085] Also, in the present embodiment, the channel information to
be used for transmitting relay data is channel information of the
above-mentioned frame. However, the channel information of several
frames before may also be used.
[0086] Also, in the present embodiment, the channel information and
the transmission signal are transmitted separately. However, they
may be transmitted in the same frame.
[0087] Also, in the case of TDD-OFDM, the base station apparatus
200 may generate the channel information from the received quality
of the uplink signal to be transmitted from mobile station
apparatus 100 to base station apparatus 200, and transmit it to
relay station apparatus 150.
[0088] Also, although in the present embodiment received intensity
was used as received quality, SIR, SNR, SINR or the amount of
interference may also be used.
[0089] Also, the target received intensity level may be set to a
received intensity level at which a desired error rate
characteristic in mobile station apparatus 100 can be
satisfied.
[0090] The timing at which relay station apparatus 150 transmits
the relay signal may be controlled in advance by control station
(not shown) which is base station apparatus 200 or an upper level
station, in such a way that this timing should not overlap with the
transmission timing of the signal that base station apparatus 200
transmits to mobile station apparatus 100.
[0091] Also, with respect to the selection of relay station
apparatus 150, base station apparatus 200, an upper level control
station apparatus or mobile station apparatus 100 may select a
relay station apparatus with excellent received quality.
[0092] Also, a power control section that controls the power
intensity for each subcarrier may further be provided. The
diversity effect at the mobile station may be calculated by the
relay station apparatus and the power may be controlled so as to
reach a predetermined target level. According to the method for
calculating the diversity effect, the power may be controlled such
that the power level for each selected subcarrier is kept equal to
or higher than an intensity level obtained by deducting an
intensity level at which the subcarrier is actually received by the
mobile station from a target level for reception by the mobile
station. Also, the power intensity for each subcarrier obtained by
the above deduction may be set to a lowest level, and the power
intensity may be increased from that level with a fixed margin.
Also, the power may be controlled in accordance with the
characteristics of the propagation path between the mobile station
and the relay station. The power level may also be controlled in
accordance with the remaining battery power of the relay
station.
[0093] Also, the subcarrier selection information may be
transmitted from the base station or the mobile station, received
by the relay station and held as subcarrier selection information
in the subcarrier selection information storage section.
[0094] Also, the subcarrier selection information may be updated at
regular time intervals or upon reception of a fixed number of relay
frames.
[0095] Also, the subcarrier selection information may be held for
each relay frame (a single frame or a plurality of frames).
[0096] Also, the relay data extraction section may be configured to
include the subcarrier selection information storage section.
Embodiment 2
[0097] In the present embodiment, an example is shown that a relay
station apparatus relays a subcarrier signal having low received
quality of the signal from a base station apparatus in a mobile
station apparatus, by means of a subcarrier having high received
quality of the signal from the relay station apparatus in the
mobile station apparatus.
[0098] As shown in FIG. 10, a mobile communication system according
to the present embodiment is comprised of mobile station apparatus
100, relay station apparatus 160 and base station apparatus
200.
[0099] Next, the overall processing will be described using the
sequence diagram shown in FIG. 11.
[0100] Processings (1) to (4) are the same as those described in
embodiment 1 (FIG. 2), and processings (1) to (4) are repeated for
as many times as the number of frames. In the example shown in FIG.
11, the processings are repeated over 3 frames.
[0101] Next, mobile station apparatus 100 generates channel
information in which the received quality of the signal transmitted
from relay station apparatus 160 is assigned a level, and transmits
the information to base station apparatus 200 (processing (5)).
Base station apparatus 200 relays this channel information, as
well, to relay station apparatus 160 (processing (6)). From the
signals received from base station apparatus 200, relay station
apparatus 160 combines, by changing the mapping of the subcarriers,
the signals addressed to mobile station apparatus 100 of as many
subcarriers as the plurality of frames which are designated to be
relayed as channel information, and relay-transmits them to mobile
station apparatus 100 as frame 4 (processing (7)).
[0102] FIG. 12 to FIG. 14 are diagrams for describing the
processing concept in the present embodiment. Similar to embodiment
1, received intensity level is used as received quality. In FIG.
12, frames 1 to 3 are frame signals sequentially transmitted by
base station apparatus 200 to mobile station apparatus 100 and
relay station apparatus 160, and, in FIG. 14, frame 4 shows a frame
signal transmitted by relay station apparatus 160, which combines
the frame signals of these frames 1 to 3 by changing the mapping of
the subcarriers, to mobile station apparatus 100.
[0103] FIGS. 12(a) to (c) show the received intensity level for
each subcarrier in mobile station apparatus 100, of the signal
transmitted from base station apparatus 200 using the frames 1 to 3
in processing (1) of FIG. 11. Also, FIGS. 12(d) to (f) show the
received intensity level for each subcarrier in relay station
apparatus 160, of the signal transmitted from base station
apparatus 200 using the frames 1 to 3 in processing (2) of FIG. 11.
Also, FIG. 13 shows the received intensity level for each
subcarrier in mobile station apparatus 100, of the signal
transmitted from relay station apparatus 160. The received
intensity level shown in FIG. 13 is measured before the frame 4 is
transmitted, and is transmitted in processing (5) and processing
(6) of FIG. 11. FIG. 14 shows the received intensity level for each
subcarrier in mobile station apparatus 100, of the relay signal
transmitted by relay station apparatus 160 using frame 4 in
processing (7) of FIG. 11.
[0104] As shown in FIGS. 12(a) to (c), in processing (1) of FIG.
11, the received intensity level of the fifth and seventh
subcarriers in frame 1, the second and fifth subcarriers in frame
2, the third and fifth subcarriers in frame 3 does not reach a
target received intensity level and the received quality is low.
Accordingly, relay station apparatus 160 extracts, from the signal
received from base station apparatus 200, and relay-transmits the
signals of the fifth and seventh subcarriers in FIG. 12(d), the
second and fifth subcarriers in FIG. 12(e), and of the third and
fifth subcarriers of FIG. 12(f).
[0105] Also, in accordance with the channel information between the
relay station apparatus and the mobile station apparatus (FIG. 13),
relay station apparatus 160 selects a subcarrier at which the
received intensity level reaches a threshold value, as a subcarrier
to be used for relay-transmission. In FIG. 13, since the received
quality of subcarriers other than the second and the sixth
subcarriers is high, relay station apparatus 160 selects the first,
third, fourth, fifth, seventh and eighth subcarriers as subcarriers
for relay-transmission. As shown in FIG. 14, relay station
apparatus 160 allocates the relay signals extracted in FIGS. 12(d),
(e) and (f) to relay-transmission subcarriers which differ from one
another, and generates frame 4 which is a relay frame. Thus, since
the subcarrier signals extracted over a plurality of times are
allocated to subcarriers which differ from one another, relay
transmission data can be transmitted at one time, so that it is
possible to reduce the number of transmissions from the relay
station apparatus and reduce transmission power.
[0106] In FIG. 14, the fifth and seventh subcarrier signals in FIG.
12(d) are mapped to the seventh and eighth subcarriers of frame 4,
the second and fifth subcarrier signals in FIG. 12(e) are mapped to
the fourth and fifth subcarriers of frame 4, the third and fifth
subcarrier signals in FIG. 12(f) are mapped to the first and third
subcarriers of frame 4, respectively.
[0107] In the example shown in FIG. 14, according to the mapping
method, allocation is made in decreasing order of the subcarriers
of frame 4, in the order of frame 1, frame 2, frame 3, and in the
descending order of the subcarriers. Also, allocation may be made
in the increasing order of the subcarriers.
[0108] Mobile station apparatus 100 shares, in advance, a mapping
method in which, mapping information relating to which subcarrier
of which relay signal (frames 1 to 3) is allocated to which
subcarrier of the relay frame (frame 4) is set to be received from
separate relay station apparatus 160, or to be transmitted to relay
station apparatus 160.
[0109] When a mapping method is shared, since mobile station
apparatus 100 and relay station apparatus 160 share two kinds of
information, which are the channel information between base station
apparatus and mobile station apparatus and the channel information
between relay station apparatus and mobile station apparatus, the
mobile station apparatus 100 can estimate how mapping is carried
out by relay station apparatus 160. Accordingly, mobile station
apparatus 100 can combine the signal transmitted from base station
apparatus 200 and the signal relay-transmitted from relay station
apparatus 160.
[0110] FIG. 15 is a block diagram showing a configuration of relay
station apparatus 160 according to the present embodiment. The same
elements as those of FIG. 6 are designated by the same numerical
symbols, and description thereof is hereby omitted.
[0111] Channel information extraction section 51 extracts the
channel information from the received signal. The extracted channel
information includes channel information between base station
apparatus 200 and mobile station apparatus 100, and channel
information between relay station apparatus 160 and mobile station
apparatus 100. The channel information between base station
apparatus 200 and mobile station apparatus 100 is inputted to relay
subcarrier selection section 53. The channel information between
relay station apparatus 160 and mobile station apparatus 100 is
inputted to relay transmission subcarrier selection section 52.
[0112] In accordance with the channel information between base
station apparatus 200 and mobile station apparatus 100, relay
subcarrier selection section 53 selects, from the signal
transmitted from base station apparatus 200 to mobile station
apparatus 100, a subcarrier of low received quality which needs to
be relayed. Then, relay subcarrier selection section 53 inputs the
information of the subcarrier which has been selected as requiring
relaying, to relay data extraction section 33.
[0113] Relay data extraction section 33 extracts the signal of the
selected subcarrier from the signal addressed to mobile station
apparatus 100, and creates relay data. The relay data is inputted
to relay data buffer 54.
[0114] If the amount of relay data has exceeded a fixed amount or,
after a regular interval has passed, relay data buffer 54 inputs
the relay data to subcarrier allocation section 35 at one time.
[0115] Relay transmission subcarrier selection section 52 selects a
subcarrier having high received quality between relay station
apparatus 160 and mobile station apparatus 100, in accordance with
the channel information between relay station apparatus 160 and
mobile station apparatus 100, and sets it as the subcarrier for
relay-transmission. The information of the selected
relay-transmission subcarrier is inputted to subcarrier allocation
section 35. Subcarrier allocation section 35 allocates relay data
to the relay transmission subcarrier.
[0116] Next, the flow of the relay processing according to the
present embodiment will be described using FIG. 16.
[0117] First, in ST (step) 161, channel information extraction
section 51 extracts the channel information.
[0118] In ST162, relay subcarrier selection section 53 judges, for
each subcarrier, from the channel information, whether the received
quality is low (whether the received intensity level is less than a
target received intensity level), and selects the subcarrier with
low received quality. Then, in ST163, it is judged whether a
subcarrier having low received quality exists. When there is no
subcarrier in ST163 which has low received quality, the flow
proceeds to ST167. On the one hand, in the case that in ST163,
there is a subcarrier with low received quality, the flow proceeds
to ST164.
[0119] In ST164, relay data extraction section 33 carries out
extraction processing for extracting a signal allocated to the
subcarrier selected in ST162 from the signal addressed to mobile
station apparatus 100.
[0120] In ST165, 166 and 167, the processings in relay data buffer
54 are carried out.
[0121] In ST165, relay data extraction section 33 stores the relay
data extracted in ST164 into relay data buffer
[0122] In ST166, relay data buffer 54 compares the amount of the
stored relay data with a threshold value, and if the amount of
relay data is larger than the threshold value, the flow proceeds to
ST168, and if it is equal to or smaller than the threshold value,
the flow proceeds to ST167.
[0123] In ST167, relay data buffer 54 checks the storage period of
the relay data in relay data buffer 54, and if the storage period
of the oldest data amongst the stored relay data is larger than a
maximum storage period, the flow proceeds to ST168, and if it is
equal to or smaller than the maximum storage period, the flow
proceeds to ST161 to wait for the reception of the next frame.
[0124] In ST168, relay transmission subcarrier selection section 52
judges the received quality for each subcarrier, from the channel
information between relay station apparatus 160 and mobile station
apparatus 100, and decides the subcarrier to be used for
transmission.
[0125] Then, in ST169, subcarrier allocation section 35 carries out
allocation processing to the subcarrier.
[0126] In the present embodiment, since relay station apparatus 160
relays by means of a subcarrier having excellent reception
characteristics between relay station apparatus 160 and mobile
station apparatus 100, the received quality of mobile station
apparatus 100 can be improved, and further, since the relay signals
of a plurality of frames can be transmitted at one time, the number
of transmissions from relay station apparatus 160 can be reduced.
Thus, it is possible to reduce the number of times of operating the
transmission amplifier for relay, and the power consumption of the
relay station apparatus can be reduced.
[0127] In the present embodiment, the channel information generated
from the received quality between relay station apparatus 160 and
mobile station apparatus 100 becomes necessary. In the above
description, it was described that this channel information is
transmitted from mobile station apparatus 100, via base station
apparatus 200. However, it may also be transmitted directly from
mobile station apparatus 100 to relay station apparatus 160.
[0128] Also, in the case of TDD-OFDM, similar to embodiment 1,
instead of the channel information between base station apparatus
200 and mobile station apparatus 100, channel information may be
generated from the received quality between mobile station
apparatus 100 and base station apparatus 200, which has been
measured by base station apparatus 200, and may be directly
transmitted from base station apparatus 200 to relay station
apparatus 160. Also, the channel information between relay station
apparatus 160 and mobile station apparatus 100 may be generated
from the received quality between mobile station apparatus 100 and
relay station apparatus 160. When the channel information is not
generated by mobile station apparatus 100, relay station apparatus
160 transmits the channel information or the mapping results to
mobile station apparatus 100, to share the mapping information of
the subcarrier, and makes it easy to understand which relay signal
is allocated to which subcarrier in mobile station apparatus
100.
Embodiment 3
[0129] The present embodiment shows an example that a plurality of
relay station apparatuses relay their respective managing
subcarriers only.
[0130] As shown in FIG. 17, a mobile communication system according
to the present embodiment is comprised of mobile station apparatus
100, a plurality of relay station apparatuses 170-1 and 170-2, and
base station apparatus 200.
[0131] Next, a description will be given of the overall processing,
using the sequence diagram shown in FIG. 18. The base station
apparatus 200 transmits a signal to mobile station apparatus 100
(processing (1)). At this time, relay station apparatus 170-1 and
relay station apparatus 170-2, as well, receive the signal
transmitted from base station apparatus 200 (processings (2) and
(3)). Next, mobile station apparatus 100 generates channel
information which has assigning leveled received quality, and
reports the channel information between this base station apparatus
200 and mobile station apparatus 100 to base station apparatus 200
(processing (4)). Base station apparatus 200 reports this channel
information to relay station apparatus 170-1 and relay station
apparatus 170-2 (processing (5) and (6)). Relay station apparatus
170-1 and relay station apparatus 170-2 relay-transmit, to mobile
station apparatus 100, a signal, from the signals received from
base station apparatus 200, which is addressed to mobile station
apparatus 100 and having the subcarriers which are each managed and
are designated as required to be relayed in accordance with the
channel information, in synchronization with each other
(processings (7) and (8)). Thus, relay station apparatus 170-1 and
relay station apparatus 170-2 transmit signals in synchronization
with each other, and thus, mobile station apparatus 100 can receive
the signal from relay station apparatus 170-1 and the signal from
relay station apparatus 170-2 around the same time, which makes it
possible to merge the plurality of received signals and improve
processing efficiency.
[0132] Next, an example illustrating the received intensity level
of the received signal at mobile station apparatus 100 and relay
station apparatuses 170-1 and 170-2 is shown in FIGS. 19A to F.
Similarly with embodiment 1, the received intensity level is used
as the received quality.
[0133] FIG. 19A shows, the received intensity level for each
subcarrier in mobile station apparatus 100, of the signal
transmitted by base station apparatus 200 in processing (1) of FIG.
18, FIG. 19B shows the received intensity level for each subcarrier
in relay station apparatus 170-1, of the signal transmitted by base
station apparatus 200 in processing (2) of FIG. 18, FIG. 19C shows
the received intensity level for each subcarrier in relay station
apparatus 170-2, of the signal transmitted by base station
apparatus 200 in processing (3) of FIG. 18, FIG. 19D shows the
received intensity level for each subcarrier in mobile station
apparatus 100, of the signal transmitted by relay station apparatus
170-1 in processing (7) of FIG. 18, FIG. 19E shows the received
intensity level for each subcarrier in mobile station apparatus
100, of the signal transmitted by relay station apparatus 170-2 at
processing (8) of FIG. 18, and FIG. 19F shows the received
intensity level for each subcarrier after signal combination in
mobile station apparatus 100, respectively. The received intensity
level differs for each subcarrier depending on the influence of
frequency selective fading propagation path.
[0134] Relay station apparatus 170-1 is set in advance to manage
the second, fourth, sixth and eighth subcarriers, and relay station
apparatus 170-2 is set in advance to manage the first, third, fifth
and seventh subcarriers. As shown in FIG. 19A, the received quality
of the second, fifth and seventh subcarriers, from the signal
transmitted from base station apparatus 200 to mobile station
apparatus 100, does not reach a target received intensity level,
and received quality is low. Relay station apparatus 170-1 and
relay station apparatus 170-2 relay a signal of the managing
subcarrier, from amongst these subcarriers. Accordingly, relay
station apparatus 170-1 relays the second subcarrier as shown in
FIG. 19D, and the relay station apparatus 170-2 relays the fifth
and seventh subcarriers as shown in FIG. 19E. Mobile station
apparatus 100 combines the signals transmitted from relay station
apparatus 170-1 and relay station apparatus 170-2 to mobile station
apparatus 100.
[0135] Next, the configuration of relay station apparatuses 170-1
and 170-2 will be described. FIG. 20 is a block diagram showing the
configuration of relay station apparatuses 170-1 and relay station
apparatus 170-2 according to the present embodiment. Relay station
apparatuses 170-1 and 170-2 employ the same configuration. Elements
which are the same as those of FIG. 6 are designated by the same
numerical symbols and description thereof is hereby omitted.
[0136] Managing subcarrier information extraction section 72
extracts the number of subcarriers managed by each relay station
and inputs it to subcarrier selection section 71. Subcarrier
selection section 71 selects from amongst the managing subcarriers
a subcarrier, having low received quality, in accordance with the
channel information, and inputs the number of the selected
subcarrier to relay data extraction section 33 and subcarrier
allocation section 35.
[0137] Next, the flow of the relay processing according to the
present embodiment will be described using FIG. 21.
[0138] First, in ST (step) 171, channel information extraction
section 31 carries out processing to extract channel
information.
[0139] In ST172, managing subcarrier information extraction section
72 carries out processing to extract subcarrier information which
is managed locally.
[0140] In ST173, subcarrier selection section 71 judges, from the
channel information, whether the received quality for each
subcarrier is low (whether the received intensity level is less
than a target received intensity level), and selects the subcarrier
with low received quality. Then, in ST174, it is judged whether
among the managing subcarriers there are subcarriers of low
received quality. When there are no subcarriers with low received
quality in ST174, the relay data generation processing is ended. On
the other hand, if there is a subcarrier with low received quality
in ST174, the flow proceeds to ST175.
[0141] In ST175, relay data extraction section 33 carries out an
extraction processing to extract, from the signals addressed to
mobile station apparatus 100, a signal allocated to the subcarrier
selected in ST173.
[0142] In ST176, subcarrier allocation section 35 carries out an
allocation processing to allocate relay data extracted in ST175 to
the same subcarrier as the subcarrier to which this relay data was
allocated at the time of transmission from base station apparatus
200.
[0143] Thus, in the present embodiment, since relaying is carried
out by a plurality of relay station apparatuses, the transmission
power for one relay station apparatus can be further reduced.
[0144] The managing subcarrier to be relayed may be set by base
station apparatus 200 or an upper level control station apparatus
and reported to both relay station apparatuses 170-1 and 170-2, or
may be set by mobile station apparatus 100 and reported to both
relay station apparatuses 170-1 and 170-2. Also, the managing
subcarriers may be set as fixed, or the received quality at relay
station apparatus 170-1 and the received quality at relay station
apparatus 170-2 may be compared for each subcarrier, and the
apparatus with the higher received quality for each subcarrier may
be set as the managing apparatus.
[0145] Also, the respective relay station apparatuses may carry out
transmission at separate timings, instead of in synchronization,
during the relay by the respective relay station apparatuses.
[0146] Also, as shown in embodiment 2, the subcarriers at the time
of relaying may be replaced by subcarriers with high received
quality.
Embodiment 4
[0147] The present embodiment shows an example in which a plurality
of relay station apparatuses carry out relay, and at least one
relay station apparatus from amongst this plurality of relay
station apparatuses relays all the subcarriers received from the
base station apparatus, and the other relay station apparatuses
supplementarily relay part of the subcarriers with low received
quality in the mobile station apparatus.
[0148] As shown in FIG. 22, a mobile communication system according
to the present embodiment is comprised of mobile station apparatus
100, a plurality of relay station apparatuses 180-1 and 180-2, and
base station apparatus 200.
[0149] Next, the overall processing will be described using the
sequence diagram shown in FIG. 23.
[0150] Base station apparatus 200 transmits a signal of frame 1 to
relay station apparatus 180-1 and relay station apparatus 180-2
(processings (1) and (2)). Relay station apparatus 180-1 and 180-2
simultaneously relay the signal of frame 1 received from base
station apparatus 200, to mobile station apparatus 100 (processings
(3) and (4)) Mobile station apparatus 100 transmits the channel
information of the signal from relay station 180-1 in mobile
station apparatus 100 to relay station 180-2 (processing (5)).
Next, base station apparatus 200 transmits the signal of frame 2 to
relay station apparatus 180-1 and relay station apparatus 180-2
(processings (6) and (7)). Relay station apparatus 180-1 transmits
the signal of frame 2 to mobile station apparatus 100 (processing
(8)). Relay station apparatus 180-2 transmits only the subcarrier
with low received quality to mobile station apparatus 100, in
accordance with the channel information between relay station
apparatus 180-1 and mobile station apparatus 100 in frame 1
(processing (9)).
[0151] Next, an example showing the received intensity level of the
received signal by mobile station apparatus 100 and relay station
apparatuses 180-1 and 180-2 is illustrated in FIGS. 24A to F.
Similar to the embodiment 1, the received intensity level is used
as received quality.
[0152] FIG. 24A shows the received intensity level for each
subcarrier in relay station apparatus 180-1, of the signal
transmitted by base station apparatus 200 in processing (1) of FIG.
23; FIG. 24B shows the received intensity level for each subcarrier
in relay station apparatus 180-2, of the signal transmitted by base
station apparatus 200 in processing (2) of FIG. 23; FIG. 24C shows
the received intensity level in mobile station apparatus 100, of
the signal transmitted from relay station apparatus 180-1 in
processing (3) in FIG. 23; FIG. 24D shows the received intensity
level in mobile station apparatus 100, of the signal transmitted
from relay station apparatus 180-2 in processing (4) of FIG. 23;
FIG. 24E shows the received intensity level at the time mobile
station apparatus 100 receives the signal from relay station
apparatus 180-1 and the signal from relay station apparatus 180-2;
and FIG. 24F shows the received intensity level at the time the
mobile station apparatus 100 receives only the relay signal of
relay station apparatus 180-1, respectively.
[0153] As shown in FIG. 24E, if mobile station apparatus 100
receives the signal from relay station apparatus 180-1 and the
signal from relay station apparatus 180-2, the received intensity
of the signal from relay station apparatus 180-2 is included in the
received intensity, and it is impossible to accurately judge which
subcarrier, from the signal of relay station apparatus 180-1 which
carries out relaying of all subcarriers, has poor received quality.
Therefore, in the present embodiment, the received quality of relay
station apparatus 180-1 only, as shown in FIG. 24F, is measured as
channel information to be received in processing (5) of FIG. 23. To
carry out this measurement, two types of pilot signals are
generated. One pilot is a pilot not multiplexed with the relay
signal from relay station apparatus 180-2 multiplexed with, and the
other pilot is a pilot the relay signal from relay station
apparatus 180-2.
[0154] FIG. 25 shows the two types of pilot signals according to
the present embodiment. In this figure, the pilot of the relay
signal of relay station apparatus 180-2 is not multiplexed in the
first frame of the pilot, and the pilot of the relay signal of
relay station apparatus 180-2 is multiplexed in the pilot of the
second frame, only for the subcarrier that transmits the relay
signal of relay station apparatus 180-2. Mobile station apparatus
100 generates, from the pilot of the first frame, the channel
information between relay station apparatus 180-1 and mobile
station apparatus 100, to be received in processing (5) of FIG. 23.
Also, mobile station apparatus 100 carries out channel estimation
in mobile station apparatus 100 by using the pilot of the second
frame.
[0155] Next, the configuration of relay station apparatus 180-2
that carries out supplementary relaying will be described. FIG. 26
shows a block diagram illustrating the configuration of relay
station apparatus 180-2 according to the present embodiment.
Elements which are the same as those of FIG. 6 are designated by
the same numerical symbols, and description thereof is hereby
omitted.
[0156] Subcarrier selection section 61 selects a subcarrier with
low received quality, in accordance with the channel information,
and inputs the number of the selected subcarrier to relay data
extraction section 33, pilot selection section 62 and subcarrier
allocation section 63. Pilot selection section 62 selects whether
or not to insert the pilot signal at a predetermined period or
predetermined timing. When the pilot signal is to be inserted, the
pilot signal is inputted to subcarrier allocation section 63.
[0157] Next, a flow of the relay processing according to the
present embodiment is described using FIG. 27.
[0158] First, in ST (step) 181, channel information extraction
section 31 carries out extraction processing of channel
information.
[0159] In ST182, subcarrier selection section 61 judges, from the
channel information, whether the received quality for each
subcarrier is low (whether the received intensity level is less
than a target received intensity level), and selects the subcarrier
with low received quality. Then, in ST183, it is judged whether
there is a subcarrier which has low received quality. When there is
no subcarrier with low received quality in ST183, the relay data
generation processing is ended. On the one hand, if there is a
subcarrier with low received quality in ST183, the flow proceeds to
ST184.
[0160] In ST184, relay data extraction section 33 carries out
extraction processing to extract a signal allocated to the
subcarrier selected in ST182, from the signal addressed to mobile
station apparatus 100.
[0161] In ST185, pilot selection section 62 judges whether it is
the period to insert the pilot signal, and if it is the period to
insert the pilot signal, the flow proceeds to ST186, and the pilot
signal is inserted to the subcarrier that is to be
relay-transmitted. On the one hand, When it is not the period to
insert the pilot signal in ST185, the flow proceeds to ST187.
[0162] In ST187, subcarrier allocation section 63 carries out
allocation processing to allocate the pilot signal and relay data
extracted in ST184 to the subcarrier.
[0163] In this way, in the present embodiment, since mobile station
apparatus 100 receives both a pilot signal that is multiplexed with
the relay signal from relay station apparatus 180-2 and a pilot
signal that is multiplexed with the relay signal, mobile station
apparatus 100 can estimate the received quality of relay station
apparatus 180-1. Therefore, since the subcarrier to be relayed can
be limited to the subcarrier with low received quality in mobile
station apparatus 100, of the signal from relay station apparatus
180-1, the transmission power of relay station apparatus 180-2 can
be reduced compared to the case of relaying all subcarriers.
[0164] In the case of TDD-OFDM, since relay station apparatus 180-1
and 180-2 can estimate the received quality between relay station
apparatuses 180-1 and 180-2 and mobile station apparatus 100, from
the uplink received quality from mobile station apparatus 100, the
pilot needs not be used as described in the present embodiment.
[0165] Also, as shown in FIG. 28, in the portion where the pilot of
relay station apparatus 180-1 and the pilot of relay station
apparatus 180-2 are multiplexed and transmitted, the pilot of the
relay station apparatus 180 alone may be transmitted. In this case,
relay station apparatus 180-1 and relay station apparatus 180-2 can
obtain channel information for each relay station apparatus.
[0166] Also, relay station apparatus 180-2 is not limited to one
mobile station apparatus but may include a plurality of mobile
station apparatuses.
[0167] Also, the multiplexing of the pilot signal may be carried
out every several symbols within a frame, or may be switched every
several frames.
[0168] In the above-described embodiments, an example has been
described in which the relay station apparatus carries out direct
communication with the base station apparatus. However, it is not
limited to this, and another relay station apparatus may further be
provided between the relay station apparatus and the base station
apparatus.
[0169] Also, an example has been described in which the first
communication apparatus is a base station apparatus, and the second
communication apparatus is a mobile station apparatus. However, the
first communication apparatus may be a mobile station apparatus and
the second communication apparatus may be a base station apparatus,
or the first communication apparatus and the second communication
apparatus may be both mobile station apparatuses.
[0170] Also, the base station apparatus, the relay station
apparatus and the mobile station apparatus may have their
respective power controlled.
[0171] Also, in the above-described embodiments, an example has
been described of a case where the present invention is configured
by hardware. However, the present invention can also be realized by
software.
[0172] Each function block employed in the description of each of
the aforementioned embodiments may typically be implemented as an
LSI constituted by an integrated circuit. These may be individual
chips or partially or totally contained on a single chip. "LSI" is
adopted here but this may also be referred to as "IC", "system
LSI", "super LSI", or "ultra LSI" depending on differing extents of
integration.
[0173] Further, the method of circuit integration is not limited to
LSI's, and implementation using dedicated circuitry or general
purpose processors is also possible. After LSI manufacture,
utilization of an FPGA (Field Programmable Gate Array) or a
reconfigurable processor where connections and settings of circuit
cells within an LSI can be reconfigured is also possible.
[0174] Further, if integrated circuit technology comes out to
replace LSI's as a result of the advancement of semiconductor
technology or a derivative other technology, it is naturally also
possible to carry out function block integration using this
technology. Application in biotechnology is also possible.
[0175] The present application is based on Japanese Patent
Application No. 2004-285468, filed on Sep. 29, 2004, the entire
content of which is expressly incorporated by reference herein.
INDUSTRIAL APPLICABILITY
[0176] The radio communication apparatus according to the present
invention provides an advantage of suppressing an increase of power
consumption when a signal is relayed from a first radio
communication apparatus to a second radio communication apparatus,
and is suitable for use in systems involving relaying operations,
such as multihop systems or the like.
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